In prior art breechblocks, the connection device between the mushroom head and the breechblock carrier forms, in the simplest case, a neck which is rigidly connected, for example, to the mushroom head and which can be pushed telescope-like into the breechblock carrier by the length of the locking distance when the breechblock is locked. However, this type of neck can also be formed on or rigidly connected to the breechblock carrier. In such an instance, the neck can be inserted into the mushroom head. Alternatively, the neck may optionally be formed from a separate part that can be inserted into both the mushroom head and the breechblock carrier.
Typically, the firearm employing the breechblock will include a locking element. The locking element is arranged fixed on the barrel. The locking element is engaged by the mushroom head when the breechblock is locked so that the recoil exerted on the mushroom head by a fired cartridge does not move the mushroom head back to a significant degree (at least not instantaneously).
Engagement between the mushroom head and the locking element can occur by means of rolls that can be swung out radially, by blocks that can be swung out radially, or by flaps or the like. Nowadays, locking mostly occurs by turning the mushroom head, which is provided with several breech pins, so that the breech pins of the head engage behind counterpins fixed in the locking element. In such an approach, automatic control of the mushroom head occurs through a guide link which operates between the mushroom head and the breechblock carrier and by support of the mushroom head in the weapon housing so that the mushroom head can only be turned when it is in its frontmost position.
Conventionally, in automatic weapons two opposite locking pins are situated in one radial plane and, optionally, at least one additional locking pin in another radial plane. However, it is also already known that several locking pins can be arranged in a single radial plane so that the mushroom head is similar in appearance to a drive shaft-gear, in which a tooth is missing at the sites prescribed for an extractor hook and/or an ejector.
Unlocking can be produced, for example, in a recoil-operated gun, by backward movement of the barrel and the entire breechblock over an initial distance. Such backward movement places the breechblock carrier in motion, subsequently rotates the mushroom head, carries out the loading movement, etc. However, a gas piston which is moved by the firing gases ejected from the barrel can also be used to in turn place the breechblock carrier in motion.
When the locking device is designed so that the mushroom head can execute a very limited backward movement during firing, then this backward motion can be applied to the breechblock carrier by a transfer mechanism, which in turn entrains the mushroom head (for example, the weapon G3).
If, in any of the described weapons, after the breechblock has been moved fully to the rear, the carrier is moved forward to feed a cartridge from a magazine or a belt device from the rear with the mushroom head, the mushroom head will be forced against the breechblock carrier in order to push the cartridge into the barrel. The forcing of the mushroom head against the breechblock carrier causes the automatic control mechanism to attempt to trigger the locking movement of the mushroom head. To prevent this locking movement from occurring, the mushroom head is guided in turn in guide tracks of the weapon housing. For example, if locking is caused by a pivotable block, the pivotable block is located to encounter a guide which prevents it from pivoting. In the common case of a rotatable mushroom head, this sits on guides that prevent its rotation.
However, in such an instance, the mushroom head and guide slide against each other under powerful mutual support so that wear is increased and the reliability of the weapon is reduced. In this regard, one need only think of the sand effect through which the uppermost cartridge in the magazine, which is forced against the magazine lip with greater force, sits even more strongly than usual. The sand effect also hampers sliding engagement between the mushroom head and guide.
This problem is addressed by German Patent No. 15 78 392 of the applicant in the special case of a semirigid, locked breechblock. The solution disclosed in that patent, however, entails several additional, precision-machined components and is, therefore, costly.
It is expressly pointed out that the ordinary longitudinal guides of the breechblock in the weapon housing are not affected by the described problem, since they need not take up any noticeable transverse forces.